Patent GB-520922-A (GB)
Title: Device for automatic adjustment of the length of a rod
IPC: B61H15/00
Filed: 1939-01-02
Abstract: 520,922. Locking rods ; adjustable links. SOC. GENERALE ISOTHERMOS. Jan 2, 1939, No. 8. Convention date, Jan. 14, 1938. [Class 80 (iii)] [Also in Group XXXIV] An automatically extensible and contractible link for use particularly as a slack adjusting device for brake mechanism comprises a rod part slidable in a tubular part and wedging rollers for coupling the parts but normally disengaged so that if the slack is insufficient the link is extended until engagement of the rollers is effected by movement of a sleeve relatively to the link by engagement with an abutment while if due to wear of the brake blocks, the slack is excessive, the sleeve is moved further and its return under spring action during release of the brakes effects shortening of the link through a second wedging roller clutch. A third wedging roller clutch normally prevents contraction of the link. The tubular part 2 of the link shown as connected to a vehicle brake operating lever has secured thereto a number of abutments 5 with inclined surfaces between which and flat faces of the rod part of the link are wedging rollers 7 separated by partitions 31. Rollers 8 between the rod 1 and an oppositely inclined abutment 6 are normally engaged to prevent contraction of the link. A sleeve 15 slidable on the tube 2 has an end cap 10 which under the action of a spring 17 normally abuts on a cage 11a for the rollers 8 slidable on the rod 1 and thus engages the rollers 8 and disengages the rollers 7 as shown. Integral with the cap 10 is a cage 11 for rollers 26, the abutment 27 of which is acted upon by a spring 28 seated in an extension 15' of the sleeve 15. In an application of the brakes the link moves in the direction of the arrow f, the movement of the tube 2 being at first transmitted to the rod 1 through the spring 17, sleeve 15, spring 28 and roller device 26, 27. When the parts have travelled a distance -corresponding to the normal play between the brake blocks and the wheels, the sleeve 15 engages an external abutment and the initial displacement of the tube 2 relatively' thereto enables a spring 9 to engage the rollers 7 with the abutments 5 and to disengage the rollers 8 from these abutments 6, whereby the force is transmitted from the tube 2 to the rod 1 by the rollers 7. If the play between the brake blocks and wheels is excessive the' sleeve 15 is further relatively displaced and during its return movement under the action of the spring 17 which has been compressed, it slides the rod 1 into the tube 2 by means of the roller clutch 26, 27. If the blocks engage the wheels before the sleeve 15 engages its abutment, the rod 1 is pulled out of the tube 2. the clutching action of the device 26, 27 being insufficient to prevent this; when however, the abutment is engaged the rollers 7 become engaged with their abutments 5 as above described to lock the rod to the tube to transmit the braking pressure. If the play is normal. the blocks engage the wheels when the sleeve 15 engages the abutment and the rod 1 is pulled out of the tube to a slight extent until the rollers 7 become engaged with the abutments 5; during the release of the brakes the rod is moved back into the sleeve by the same amount, by the sleeve 15 and clutch 26, 27. In the arrangement shown, the part 2 of the link is connected to one end of one of a pair of brake levers which are interconnected for simultaneous operation by a link and the abutment for the sleeve 15 is formed by one end of the second lever and is engaged by the sleeve through a rod secured by its forked end 12 to the sleeve.